1. Field of the Invention
The present invention relates to a tool changing device for a machine tool and a method of cleaning tools held by a turret or magazine of the tool changing device.
2. Description of the Related Art
In changing a tool of a machine tool, machining accuracy of a workpiece is maintained by properly fitting and attaching the tool to a spindle of the machine tool. In a machine tool having a tool changing device, however, tools held by a turret or a magazine are arranged close to a machining area where a workpiece is cut. Therefore, there is a high possibility that swarf produced by cutting of a workpiece is adhered to the tools held by the turret or the magazine. If foreign matter, such as swarf, is adhered to a contact surface of the tool with the spindle, a tool holder may not be properly fitted to the spindle, which affects the machining accuracy. For this reason, the method generally employed is one in which a taper portion and a flange portion of the tool, which are contact surfaces to be in contact with the spindle, are cleaned by removing swarf and the like therefrom using fluid, such as air and coolant liquid.
For instance, there is a well-known method in which after a tool is detached from a spindle and stored in a tool magazine, the swivel plate of the tool magazine is rotated. A tool-holding portion holding the detached tool is then transferred to the position in which tool-cleaning means is arranged, thereby cleaning the tool by cleaning liquid (JP 2001-198761A).
There is also a well-known cleaning device in which when a tool is fitted to a spindle in a tool changing process, coolant is sprayed onto the taper of the tool, which is tightly fitted to the tapered face of the spindle, to thereby remove and clean up the adhered swarf and the like (JP 2002-273640A).
Moreover, there is another known device in which when the flange face of a tool is brought into contact with the end face of a spindle, and at the same time a double fit-type tool for fitting a shank portion into the fitting hole of the spindle is utilized, a tool for cleaning the spindle end face is provided and fixed to the spindle, leaving a space between the spindle end face and the flange face of the tool for cleaning the spindle end face. Cleaning liquid is supplied to the space, which removes foreign matter, such as swarf, from the spindle end face and thus cleans the spindle end face (JP 2001-18144A).
There is further another known device in which an air nozzle is arranged to open in the tapered portion of a spindle, which is to be fitted to the tapered portion of a tool holder. In detaching a tool holder from the tapered portion of the spindle or when a new tool is attached to the spindle, the pressurized air is supplied from a pressurized air supply onto the contact face of the tool holder and that of a spindle taper hole through an air hole formed at the spindle and the air nozzle. Thus, swarf and the like adhered to the tapered portions of fitting faces of the tool holder and spindle are removed and cleaned up by using air (JP 52-49579A).
The turret and magazine of the tool changing device are arranged near a cutting area. Therefore, the swarf scattered during machining is adhered to the tapered portion and flange portion of the tool that is accommodated and held by the turret or magazine. As a result, even if the tapered portion and flange portion of the tool, which are contact faces to be in contact with the spindle, are cleaned after the use of the tool, foreign matter, such as swarf, is adhered thereto during a standby period. If the tool is attached to the spindle and used with the foreign matter adhered thereto, there occur problems that the machining accuracy is deteriorated and that the spindle and the tapered and flange portions of the tool get scratches. Such problems are likely to be considered to be solved if only the contact faces, namely the tapered portion and the flange portion, which are to be in contact with the spindle, are cleaned right before the use of the tool as described in JP 2001-198761A and JP 52-49579B.
In case that the machining is performed using coolant, however, swarf adhered to a standby tool in the turret or magazine adheres persistently to the tapered or flange portion of the tool in time due to the concentrated high-viscosity coolant. Even the cleaning process using the coolant or the like cannot completely remove such swarf.
Likewise, in case of dry machining or machining using air, the amount of swarf adhered to the tool in the turret or magazine is increased by static electricity and the like, so that it is impossible to completely remove the swarf by performing the cleaning process using air.